The present invention relates to fragrance precursors for a fragrant ketone and a fragrant ester. Compositions containing such fragrant precursors are also provided. A process for imparting a fragrance to a substrate using such a fragrance precursor is also provided.
A principal strategy currently employed in imparting odors to consumer products is the admixing of the fragrance directly into the product. There are, however, several drawbacks to this strategy. The fragrance material can be too volatile and/or too soluble, resulting in fragrance loss during manufacturing, storage, and use. Many fragrance materials are also unstable over time. This again results in loss during storage.
In many consumer products it is desirable for the fragrance to be released slowly over time. Microencapsulation and inclusion complexes with cyclodextrins have been used to help decrease volatility, improve stability and provide slow-release properties. However, these methods are, for a number of reasons, often not successful. In addition, cyclodextrins can be too expensive.
Precursors for the delivery of organoleptic compounds, especially for flavors, fragrances and masking agents are described in EP-A 0 936 211. This delivery system releases one or more odoriferous compounds upon exposure to light and/or UV irradiation. Using this system in various consumer products leads to a prolonged perception of the fragrant compound(s) to be released.
WO 99/60990 describes fragrance precursors which release fragrant alcohols, aldehydes or ketones upon exposure to light. Perfuming compositions containing these fragrance precursors can be used in various consumer products such as detergents, fabric softeners, household products, hair care products, etc.
It is known that phenacyl glycosides undergo a Norrish Type II photoreaction leading to gluconolactones and the corresponding phenacyl compound (Crich et al., Tetrahedron, 1995, 51, 11945-11952). However, it has not been described or suggested to use such phenacyl acetals as fragrance precursors, which are capable of releasing a fragrant ketone and a fragrant ester over a prolonged period.
Many fragrant compounds with odors accepted by the public are esters of high volatility resulting in a short period of perceivable odor. Such esters are quickly hydrolyzed in an alkaline environment, thereby losing the fragrant characteristic. Therefore, they are of limited use for laundry products.
It is therefore desirable to have a fragrance delivery system which is capable of releasing the fragrant compound or compounds in a controlled manner, while maintaining a desired odor over a prolonged period of time.
An object of the present invention is to provide non-volatile precursors for volatile fragrant esters.
Another object of the present invention is to provide fragrance precursors which are stable in an alkaline environment, especially in laundry products.
A further object of the present invention is to provide fragrance precursors with high substantivity.
Another object of the present invention is to provide fragrance precursors which are activated and cleaved by light.
A further object of the present invention is to provide fragrance precursors with slow release properties.
Accordingly, one embodiment of the invention is a fragrance precursor of formula I: 
for a fragrant ketone of formula II: 
and a fragrant ester of formula III: 
wherein,
R1 to R5 represent independently H, xe2x80x94NO2, linear or branched C1-C6-alkyl, C1-C6-alkenyl, C1-C6-alkinyl, or C1-C4-alkoxy,
R6 and R7 are independently H, linear or branched C1-C6-alkyl-, C1-C6-alkenyl, or C1-C6-alkinyl,
R8 and R9 are the residues of an acid R8-COOH and an alcohol R9OH respectively forming the fragrant ester of formula III.
Another embodiment of the invention is a composition containing a base and a fragrance precursor of formula I: 
that upon exposure to light forms a fragrant ketone of formula II: 
and a fragrant ester of formula III: 
wherein,
R1 to R5 represent independently H, xe2x80x94NO2, linear or branched C1-C6-alkyl, C1-C6-alkenyl, C1-C6-alkinyl or C1-C4-alkoxy,
R1 and R2, R2 and R3, R3 and R4, and R4 and R5 may form together one or two aliphatic or aromatic rings,
R6 and R7 are independently H, linear or branched C1-C6-alkyl-, C1-C6-alkenyl, C1-C6-alkinyl, and
R8 and R9 are the residues of an acid R8-COOH and an alcohol R9OH respectively forming the fragrant ester of formula III.
A further embodiment of the invention is a process for providing a fragrance to a substrate having the steps of:
(a) contacting a substrate with a composition comprising fragrance precursor of formula I: 
wherein,
R1 to R5 represent independently H, xe2x80x94NO2, linear or branched C1-C6-alkyl, C1-C6-alkenyl, C1-C6-alkinyl or C1-C4-alkoxy,
R1 and R2, R2 and R3, R3 and R4,and R4 and R5 may form together one or two aliphatic or aromatic rings,
R6 and R7 are independently H, linear or branched C1-C6-alkyl-, C1-C6-alkenyl, C1-C6-alkinyl, and
R8 and R9 are the residues of an acid R8xe2x80x94COOH and an alcohol R9OH respectively forming the fragrant ester of formula III; and
(b) exposing the substrate to light source, to form a fragrant ketone of formula II: 
and a fragrant ester of formula III: 
The present invention relates to fragrance precursors of formula I: 
which upon exposure to light, and in particular daylight, release a fragrant ketone of formula II: 
and a fragrant ester of formula III: 
wherein
R1 to R5 represent independently H, xe2x80x94NO2, branched or linear C1-C6-alkyl, C1-C6-alkenyl, C1-C6-alkinyl, or C1-C4-alkoxy,
R1 and R2, R2 and R3, R3 and R4, and R4 and R5 may form together one or two aliphatic or aromatic rings, these rings may optionally contain branched or linear C1-C4-alkyl, C1-C4-alkenyl, or C1-C4-alkinyl residues, and the above rings and residues may contain one or more oxygen atoms,
R6 and R7 are independently H, branched or linear C1-C6-alkyl, C1-C6-alkenyl, or C1-C6-alkinyl, and R6 or R7 may form with either R1 or R5 a carbocyclic ring optionally substituted by an aliphatic residue.
R8 and R9 are the residues of an acid R8xe2x80x94COOH and an alcohol R9OH respectively forming the fragrant ester of formula III.
The branched carbon chains defined above also may have multiple branched chains.
The fragrance precursors of formula I release, upon exposure to light, volatile fragrant esters of formula III and fragrant ketones of formula II. Because the precursors of the invention are stable in an alkaline environment, and show high substantivity, they are well adapted for detergent and laundry use.
The fragrance precursors of the present invention are slowly cleaved when exposed to light, in particular daylight. Upon absorption of energy from the light, the phenacyl acetals of formula I undergo a Norrish Type II photoreaction, which leads to the release of a fragrant ketone of formula II and a fragrant ester of formula III.
The release of the above mentioned fragrant compounds occurs, for example, upon exposure to a UV radiation source, such as sunlight penetrating through ordinary windows, although the light need not be particularly rich in UV irradiation. Upon exposure to bright sunlight, in particular direct sunlight from the outdoors, the release of the fragrant compounds of formula II and III will occur faster and to a greater extent than upon exposure to room light inside a building. The cleavage of the precursors of the present invention can also be initiated by an appropriate lamp, for example, a sun tanning lamp.
The photoreaction of the fragrance precursors of formula I involves, in a first step, the absorption of light by the keto-group followed by abstraction of the acetal-H atom and subsequent cleavage of the resulting 1,4-diradical (Scheme A). It has been found that the aromatic residue of the fragrance precursors plays an important role in this photoreaction as it influences the absorption maxium xcexmax of the keto-group. Therefore, the cleavage properties of the fragrance precursors can be modified by variation of the substituents R1 to R5. 
The fragrant ketones of formula II may be used as an ingredient for the formulation of perfumes or perfumed articles using well known techniques. Non-limiting examples of aryl alkyl ketones of formula I include acetanisole (1-(4-methoxyphenyl)-ethanone) (Givaudan Roure (International) SA, Vernier, Switzerland), acetophenone (1-phenyl-ethanone) (Haarmann and Reimer GmbH, Germany), Crysolide(copyright) (4-acetyl-6-tert-butyl-1,1-dimethyl-indan) (Givaudan Roure (International) SA, Vernier, Switzerland), dimethyl acetophenone (1-(2,4-dimethylphenyl)-ethanone) (Fluka AG, Buchs, Switzerland), Fixolide(copyright) (1-(5,6,7,8-tetrahydro-3,5,5,6,8,8-hexamethyl-2-naphthalenyl-ethanone) (Givaudan Roure (International) SA, Vernier, Switzerland), Florantone T(copyright) (1-(5,6,7,8-tetrahydro-2-naphthalenyl)-ethanone) (Takasago Perfumery Co., Japan), Grassenone 34(copyright) (3-methyl-1-(4-methylphenyl)-4-hexen-1-one) (Keemia Institute, Tallin USSR), isopropylindanone (2-(1-methylethyl)-indanone) (Givaudan Roure (International) SA, Vernier, Switzerland), Lavonax(copyright) (1-phenyl-4-penten-1-one) (International Flavors and Fragrances, USA), Musk F (5-acetyl-1,1,2,3,3-pentamethyl-indane) (CNNP), Musk ketone(copyright) (4-tert-butyl-3,5-dinitro-2,6-dimethyl-acetophenone) (Givaudan Roure (International) SA, Vernier, Switzerland), Novalide(copyright) (1,6,7,8-tetrahydro-1,4,6,6,8,8-hexamethyl-indacen-3(2H)-one) (Givaudan Roure (International) SA, Vernier, Switzerland), Oranger Crystals(copyright) (1-(2-naphthalenyl)-ethanone) (Givaudan Roure (International) SA, Vernier, Switzerland), Orinox(copyright) (1-[4-(1,1-dimethylethyl)-2,6-dimethylphenyl]-ethanone) (Polak""s Frutal Works BV, Netherlands), Phantolide(copyright) (1-(2,3-dihydro-1,1,2,3,3,6-hexamethyl-1H-inden-5-yl-ethanone) (Polak""s Frutal Works BV, Netherlands), propiophenone (1-phenyl-propanone) (Haarmann and Reimer GmbH, Germany), Traseolide 100(copyright) (1-[2,3-dihydro- 1,1,2,6-tetramethyl-3-(1-methylethyl-1H-inden-5-yl-ethanone) (Quest International, Netherlands), Vernolide(copyright) (1-(5,6,7,8-tetrahydro-3xe2x80x2, 5xe2x80x2, 5xe2x80x2, 8xe2x80x2, 8xe2x80x2-penta-methyl-2-naphthalenyl)-ethanone) (Givaudan Roure (International) SA, Vernier, Switzerland), Versalide(copyright) (1-(5,6,7,8-tetrahydro-3xe2x80x2-ethyl,5xe2x80x2, 5xe2x80x2, 8xe2x80x2, 8xe2x80x2-tetramethyl-2-naphthalenyl)-ethanone) (Givaudan Roure (International) SA, Vernier, Switzerland), and Vitalide(copyright) (1-(hexahydrodimethyl-1H-benzindenyl)-ethanone) (Takasago Perfumery, Japan).
The above list is illustrative only and is not intended to limit fragrant ketones of formula II. For example, additional fragrant ketones of formula II are e.g., described in xe2x80x9cPerfume and Flavor Chemicals,xe2x80x9d S. Arctander Ed., Vol. I and II, Allured Publishing Corporation, Carol Stream, USA, 1994 and in K. Bauer, D. Garbe and H. Surburg, Eds., Common Fragrance and Flavor Materials, Wiley-VCH, 3rd Edition, Weinheim, 1997.
Fragrance esters of formula III represent an important class of perfumery raw materials and include compounds of a great structural variety. Fragrance esters of formula III contribute to the odor and aroma of nearly all fruits and are known to be useful ingredients for the formulation of perfumes or perfumed articles. In the following, a non-limiting list of such esters are given as examples.
Most of the aliphatic esters of formula III are either acetates or include ethanol as the alcohol component. Examples of such esters of formula III include amyl butyrate, butyl 2-methylpentanoate, 3,7-dimethyloctan-3-yl acetate, ethyl 2-methylbutyrate, hexyl acetate, hexyl isobutyrate, and isopropyl 2-methylbutyrate.
The lower fatty acid esters of acyclic terpene alcohols, e.g. geraniol, linalool, and citronellol, and of cyclic terpene alcohols, e.g. menthol, xcex1-terpineol, borneol, and guaiyol, are important both as fragrance and as flavor substances, and are envisaged as esters of formula III.
Various cycloaliphatic esters of formula III are widely used as perfumery chemicals, and include, for example: Agrumex(copyright) (2-tert-butylcyclohexyl acetate) (Haarmann and Reimer GmbH, Germany), Vertenex(copyright) (4-tert-butylcyclohexyl acetate) (International Flavors and Fragrances, USA), Verdylacetate(copyright) (4,7-Methano-3a,4,5,6,7,7a-hexahydro-5(6)-indenyl acetate) (Givaudan Roure (International) SA, Vernier, Switzerland), Givescone(copyright) (ethyl 2-ethyl-6,6-dimethyl-2-cyclohexenecarboxylate and ethyl 2,3,6,6-tetramethyl-2-cyclohexenecarboxylate) (Givaudan Roure (International) SA, Vernier, Switzerland), Cyclogalbanat(copyright) (allyl cyclohexyloxyacetate) (DRAGOCO Gerberding and Co. AG, Germany), Methyl jasmonate(copyright) (3-oxo-2-(cis-pentenyl)cyclo-pentaneacetic acid methyl ester) (Firmenich S.A., Switzerland), and Hedion(copyright) (methyl (3-oxo-2-pentyl-cyclopentyl)acetate) (Firmenich S.A., Switzerland).
Other important esters of formula III used in perfumery are those derived from araliphatic alcohols and aliphatic acids. Such compounds have characteristic odor properties. Important esters that fall into this category are e.g. benzyl acetate, phenethyl acetate, xcex1,xcex1-dimethylphenethyl acetate, and cinnamyl acetate.
Many of the esters of formula III described above, which are of pleasant odor, have a rather high volatility. This is especially true for aliphatic esters exhibiting typical fruity odors and for lower fatty acid esters of acyclic terpene alcohols having pleasant, citrusy, floral odors. An example of such a volatile ester is e.g. cis-3-hexenyl acetate. Cis-3-hexenyl acetate when applied to a surface of a substrate, for example, a fabric using a fabric softener in the rinsing cycle of the washing process, can only be perceived over a short period of time of one or two hours, depending on the concentration of cis-3-hexenyl acetate in the fabric softener.
The fragrance precursors of the present invention are not, or only slightly, volatile. The fragrant ketone of formula II and the fragrant ester of formula III are released only upon exposure to light, especially daylight. The photochemical cleavage provides over days and weeks perceptible amounts of the fragrant compounds. The period of release depends inter alia on the amount or concentration of the precursor applied to a substrate, the duration of exposure to light, its intensity, and its wavelength.
Fragrance esters of formula III are prone to undergo hydrolysis into an acid of formula R8COOH and an alcohol of formula R9OH, especially in alkaline products. Therefore, many fragrance accords containing such esters, e.g. fruity accords, cannot be imparted to such products.
Today""s consumers select a certain product not only based on performance but also based on the odor. From the foregoing it is evident that products for introducing a variety of fragrance accords to products having alkaline pH are desirable. The fragrance precursors of the present invention have the advantage that they are not or only slightly volatile and are chemically stable in consumer products having alkaline and neutral pH. A precursor of formula I added to, e.g., a powder detergent is stable in the detergent powder throughout storage. During the washing cycle (alkaline pH) and the rinsing cycle (neutral pH), the precursor is deposited on the fabric surface. It is only upon exposure of the fabric to light, for example during line drying in the sun, that the release of the fragrant ketone of formula II and the fragrant ester of formula III is started.
It has been noted above that esters of formula III, and especially the aliphatic ones, are rather volatile compounds. Furthermore, they are water soluble and are, therefore, lost to some extent during the washing/rinsing cycle, if introduced directly into detergents.
The fragrance precursors of formula I have the advantage that they have good substantivity on different substrates, especially on fabrics. Furthermore, the precursors are not or only slightly volatile, thus no loss occurs during storage. With the precursors of the present invention, highly volatile esters of formula III with low substantivity are successfully applied to achieve a long lasting pleasant odor. The volatile esters are produced in situ after application of the precursors of formula I onto a fabric during the washing cycle.
In the precursors of the invention, the moiety derived from a fragrant ketone of formula II brings three advantages: it introduces stability and substantivity to the precursors of formula I, and upon activation by light exhibits fragrant properties.
The fragrance precursors of the present invention are advantageously prepared via two methods. Both methods use an (xcex1-hydroxy-ketone as starting material. The latter is prepared by bromination of the corresponding fragrant ketone followed by sodium formate treatment and subsequent hydrolysis as shown in scheme I: 
According to the first method, the xcex1-hydroxy-ketone intermediate is reacted under acid conditions with a vinyl ether to the desired precursor of formula I. The vinyl ether is obtained via the acetal of an aldehyde R8CHO and an alcohol R9OH. The synthesis is illustrated in scheme II: 
According to the second method, the xcex1-hydroxy-ketone is transformed to the corresponding vinyl ether using a Hg catalyst. The vinyl ether is then coupled with the alcohol R9OH from which the fragrant ester of formula III is derived. This method allows for the use of a great variety of alcohols, i.e. residues R9 especially for allylic residues. The synthesis via this route is illustrated in scheme III: 
Preferred precursors of the present invention are compounds releasing an aliphatic ester of formula III wherein R8 is the residue of an aliphatic acid having 1 to 4 carbon atoms, and R9 is the residue of an aliphatic alcohol having 2 to 20 carbon atoms. Most preferred precursors are those releasing an ester derived from acetic acid, i.e. wherein R8 is xe2x80x94CH3.
Other preferred precursors include compounds wherein R8 is the residue of an aliphatic acid having 5 to 20 carbon atoms, and R9 is the residue of an aliphatic alcohol having 1 to 5 carbon atoms. Most preferred compounds are those releasing an ester derived from ethanol, i.e. wherein R9 is xe2x80x94CH2CH3.
Other preferred precursors include compounds wherein R8 is the residue of an aliphatic acid having 1 to 4 carbon atoms, and R9 is the residue of a terpene alcohol having 10 to 20 carbon atoms. Most preferred compounds are those wherein the alcohol is a monoterpene alcohol.
Other preferred precursors include compounds wherein R8 is the residue of a cycloaliphatic acid having 5 to 20 carbon atoms, and R9 is the residue of an aliphatic alcohol having 1 to 5 carbon atoms. Most preferred compounds are those wherein the alcohol is ethanol.
Other preferred precursors include compounds wherein R8 is the residue of an aliphatic acid having 1 to 4 carbon atoms, and R9 is the residue of an araliphatic alcohol having more than 5 carbon atoms. Most preferred precursors are those releasing an ester derived from acetic acid, wherein R8 is xe2x80x94CH3.
Other preferred precursors include compounds wherein at least one of the residues R6 or R7 is H. Most preferred are compounds wherein R6 and R7 is H. Upon cleavage of these precursors, a fragrant ketone of formula II is released wherein said ketone is an aryl methyl ketone.
Other preferred precursors include compounds wherein R6 and R7 are H, and R1 to R5 represent independently hydrogen, xe2x80x94NO2, linear or branched C1-C6 alkyl, alkenyl, alkinyl, and C1-C4 alkoxy. Most preferred compounds are those releasing a fragrant ketone of formula II wherein the fragrant ketone is selected from 1-phenyl-ethanone, 2,4-dimethylphenyl-ethanone, 1-[4-(1,1-dimethylethyl)-2,6-dimethylphenyl]-ethanone, 1-(4-tert-butyl-3,5-dinitro-2,6-dimethyl)-ethanone and 1-(4-methoxyphenyl)-ethanone. Other preferred precursors include compounds wherein R1 and R2, R2 and R3, R3 and R4, R4 and R5 form together an aliphatic or aromatic ring, wherein this ring optionally contains substituted or unsubstituted C1-C4 alkyl, alkenyl, alkinyl residues and includes one or more oxygen atoms. Most preferred compounds are those releasing a fragrant ketone of formula II wherein the fragrant ketone is selected from 1-(2-naphtalenyl)-ethanone, 4-acetyl-6-tert-butyl-1,1-dimethyl-indan, 1-(5,6,7,8-tetrahydro-3,5,5,6,8,8-hexamethyl-2-naphthalenyl-ethanone, 1-(5,6,7,8-tetrahydro-3xe2x80x2, 5xe2x80x2, 5xe2x80x2, 8xe2x80x2, 8xe2x80x2-pentamethyl-2-naphthalenyl)-ethanone, 1-(5,6,7,8-tetrahydro-3xe2x80x2-ethyl-5xe2x80x2, 5xe2x80x2, 8xe2x80x2, 8xe2x80x2-tetramethyl-2-naphthalenyl)-ethanone, 1-(2,3 -dihydro-1,1,2,3,3 ,6-hexamethyl-1H-inden-5-yl-ethanone, 1-[2,3-dihydro-1,1 ,2,6-tetramethyl-3-(1-methylethyl-1H-inden-5-yl-ethanone, 5-acetyl-1,1,2,3,3-pentamethyl-indane, and 1-(5,6,7,8-tetrahydro-2-naphthalenyl)-ethanone.
Since the compounds of formula I, upon exposure to light, are cleaved and provide a fragrant ketone of formula II and a fragrant ester of formula III, they permit the development of useful consumer products with enhanced fragrant properties, especially having long lasting pleasant odors. Therefore, the present invention also relates to the use of all compounds of formula I as precursors for fragrant compounds.
The fragrance precursors of the present invention can be used in any product in which a prolonged and defined release of the above mentioned fragrant compounds is desired. Therefore, these precursors are especially useful in functional perfumery, and in products which are exposed to sunlight, during or after application.
The compounds of the present invention can act as fragrance precursors in functional and fine perfiunery, i.e. in fine fragrances, industrial, institutional, home, and personal care products. Industrial, institutional, and home cleaning products to which the fragrance precursors can be added include all kinds of detergents, window cleaners, hard surface cleaners, all purpose cleaners, and furniture polishes. The products can be liquids or solids, such as powders or tablets. Substrates including fabrics and surfaces treated with a product containing a fragrance precursor of the present invention will diffuse a fresh and clean odor upon exposure to light much longer than when cleaned with a conventional cleaner. Fabrics or clothes washed with such detergents will release the fragrant compounds even after having been stored for weeks in a dark place, e.g. a wardrobe.
The precursors of the present invention are also useful for application in all kinds of body care products. Especially interesting products are hair care products, for example, shampoos, conditioners, and hairsprays and skin care products such as cosmetic products, and especially sun protection products.
The above mentioned examples are of course only illustrative and non-limiting. Other products to which the precursors of the present invention may be added include soaps, bath and shower gels, deodorants, and even perfumes and colognes.
The fragrance precursors of the present invention can be used alone or in combination with other fragrance ingredients, solvents, or adjuvants known to those skilled in the art. Such ingredients are described, for example, in xe2x80x9cPerfume and Flavor Chemicals,xe2x80x9d S. Arctander, Ed., Vol. I and II, Allured Publishing Corporation, Carol Stream, USA, 1994 and include fragrance compounds of natural or synthetic origin and essential oils of natural products.
The amounts in which the precursors of formula I are incorporated in the various above-mentioned products will vary. The amounts depend on the nature of the fragrant compounds to be released, the nature of the product to which the precursors are added, and the desired olfactory effect. The amounts used will also depend on the co-ingredients in a given composition when the precursors of the present invention are used in admixture with perfuming co-ingredients, solvents, or adjuvants. Typical concentrations are in the order of 0.01% to 5% by weight of the products.
The following examples are provided to further illustrate the process of the present invention. These examples are illustrative only and are not intended to limit the scope of the invention in any way.